Page 323 - Drilling Technology in Nontechnical Language
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314 Drilling Technology in Nontechnical Language Second Edition
inside the groove. However, the top of the BHA cannot move through the
groove, having a larger OD. The result is that the pipe becomes stuck at
the top of the BHA. Full circulation will be possible. If the BHA was
not pulled too hard into the keyseat, it might be possible to move the
drillstring down.
Fig. 13–3. Geometry-related stuck pipe
Keyseats can be avoided by limiting the dogleg severity of the buildup
section, limiting the number of rotating hours against the bend before it is
cased, and limiting the drillstring tension while drilling below the bend.
A tool known as a string reamer can be placed in the drillpipe above the
bend, this tool enlarges the groove as it moves downwards during drilling.
A keyseat reamer can also be run at the top of the BHA, which allows the
keyseat to be dressed out by rotating while pulling out of the hole. It takes
extra time and is a bit tricky, so it is preferable to use a string reamer,
if possible.
If a section of the hole was drilled with an assembly that caused a
dogleg to form (such as a build or steerable motor assembly), problems
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